Rachel Knight, 31, has countless stories about money being tight when she was growing up. There was the time when she was six years old and her parents couldn’t afford to take her younger sister to the doctor.

There were the mornings in the middle of January when there was neither hot water nor bath soap, so she had to take a cold shower with grainy laundry detergent. There was the teasing from kids at school who mocked the clothes she wore—the oversize, stained T-shirts that her family got for free from the church mission.

“People talk about being poor,” says Knight. “but unless you know what it’s like to go hungry so your kid sister can have the other half of the only bologna sandwich you’ll get for the day,” she says, “you don’t know a thing.”

Now Knight, a wife and mother, has a good job, and, in theory, is living the American dream. Still, though her household income is about $140K per year, neither she nor her husband has any savings.

And every month, the minimum payments on their credit cards grow closer to exceeding the cost of their mortgage. She knows she’s headed for financial disaster, yet she continues to hit the spa and download shopping apps from her favorite stores.

Knight acknowledges that her extravagant spending is likely a knee-jerk reaction to the lean years of her childhood.

Why the Poor Spend More

And she’s not alone: In fact, her spending behavior is echoed by scientific research. A recent study published in the February 2013 edition of Psychological Science suggests that, surprisingly, adults who grow up with fewer financial resources are more likely to be heavy spenders during times of economic crisis, whereas those who grew up wealthier will respond to tough times by cutting back.

One would think that someone who knows what it’s like to be less fortunate would be afraid of doing anything that might put them back in that position again, but that’s not so according to Professor Joshua Ackerman, a co-author of the study: “As adults in times of stress, particularly economic stress,” he says, “people who grew up relatively wealthy tend to be more interested in saving whereas people who grew up relatively poor tend to be more interested in spending. Although neither strategy is irrational, the spend-now strategy could create longer-term problems over people’s lives. So, if you grew up relatively poor, you may have to battle your instincts or immediate preferences in times of stress in order to ensure your long-term financial health.”

And, for Rachel Knight and others like her, often that first instinct is to whip out your wallet. “Every time I see something I want, I buy it,” Knight says. “Because if I don’t, my mind goes back to being that poor kid, living in the projects, and all I can think is, ‘I know I deserve better…’”

How to Beat “I Deserve It” Syndrome

“I deserve it” is one line with which Katie Brewer, a certified financial planner™ with LearnVest Planning Services, is very familiar.

“I hear it from people all the time,” Brewer says of her financial planning clients. “They spoil themselves as adults because they’re making up for all the ways they felt deprived as kids.”

In other words, although Knight is no longer poor, her spending habits are in danger of putting her back in the poor house.

“When I think about how my kids are growing up, I wonder if they are going to struggle with the same problems I’ve had because my parents never really saved much, and now I have nothing in my savings account,” she says.

But Brewer says Knight—and others like her—can change. “You are not your parents, and you are not your past,” she says. “Just because they went down a rocky path doesn’t mean that you have to.”

Here, the three things that Brewer says will keep you from reacting like a poor person—so you can finally live richly.

Saying “I deserve it” is one of the biggest culprits behind failed diets—and failed budgets. You see something that you want to buy (or eat) but you don’t really need, so you tell yourself no. Then that “no” starts gnawing at you and you feel deprived.

You may begin telling yourself that you’re a grown-up who can spend her money however she chooses. So you decide to treat yourself just this once. The problem, Brewer says, is that it’s never a good idea to make financial decisions based on a feeling of deprivation. Instead, she suggests turning the “I deserve” on its head.

“Establish larger, long-term savings goals,” she says, like a year-end vacation or a living-room makeover, something that will truly make you feel rich, not satiate a whim. Then, instead of telling yourself you deserve that pretty new dress, remind yourself of the bigger picture—and what you’ve chosen to save for over time.

“When someone decides one afternoon, ‘I need a new pair of shoes’ or ‘My computer is running slow, I’m just going to replace it,’” she says, “these are the kinds of decisions that can throw you way off.”

We all have the best of intentions, but it’s those last-minute, emotional purchases that often get the best of us. The next time you’re in danger of thwarting your bottom line, do a quick mental check—whether you’re about to spend $5 or $500—by asking yourself these three questions:

- Have I saved up for this?

- Do I really need this?

- Will this delay me from meeting my goals?

Still not sure how much you should be spending and saving? The 50/20/30 Rule makes budgeting easy.

Maybe for you it’s shoes, or maybe it’s kitchen gadgets. Brewer says her clients who weren’t used to having money as kids often get that feeling of cash burning a hole in their pocket when they spot something they like. And there’s nothing that’ll make them go overboard faster than a 20% off coupon.

Of course, saving $15 at the grocery store when the items on your list happen to be on sale is a good deal. Taking home a $350 sea foam green KitchenAid you had no intention of buying just because it’s on special? Well, that’s a budget bomb.

Next time you’re tempted, Brewer suggests this tip: Don’t set yourself up to spend money you wouldn’t otherwise spend. In other words, unsubscribe from retailers’ mailing lists and flash sale sites, and steer clear of places (or specific store aisles) where you might be tempted to take advantage of a deal on something you don’t need.

Of course, when you are making a planned purchase, you should always look for a bargain, just don’t let the bargain come looking for you.

LearnVest Planning Services is a registered investment adviser and subsidiary of LearnVest, Inc. that provides financial plans for its clients. Information shown is for illustrative purposes only and is not intended as investment advice. Please consult a financial adviser for advice specific to your financial situation. The people quoted in this piece are not clients of LearnVest Planning Services.